Try this:
public static List<ProductActivity> getCatalog(Resources res){
if(catalog == null) {
catalog.add(new Product("Dead or Alive", res
.getDrawable(R.drawable.product_salmon),
"Dead or Alive by Tom Clancy with Grant Blackwood", 29.99));
catalog.add(new Product("Switch", res
.getDrawable(R.drawable.switchbook),
"Switch by Chip Heath and Dan Heath", 24.99));
catalog.add(new Product("Watchmen", res
.getDrawable(R.drawable.watchmen),
"Watchmen by Alan Moore and Dave Gibbons", 14.99));
}
}